Jumat, 23 September 2011

Indonesian Bathymetric layer in IMG format

Dear Prienz,

After searching for free bathymetry data for Indonesia, it seems that the multibeam bathymetric data is the best free data source, but unfortunately it does not cover the whole Indonesia. From all free sources, the easiest way is to download it from GEBCO (General Bathymetric Chart of the Ocean), they provide the data of world bathymetry for free. You can download it from here, but you are required to be a registered BODC web user, don't worry, its free.

I use the 'The GEBCO_08 Grid' (30 arc-second) and process it into *.IMG format. This 30arc second ocean depth data is not as good as the aster gdem land altitude data. So, dont be surprised if the beach line is not really accurate.The original data from GEBCO is shown below:

Original data from GEBCO

The theory that Indonesian islands, millions of years ago, used to be part(joined) of two continents could be true, you can see from the color of ocean depth. During ice age, possibly we could walk to neighboring countries. The theory can then continue and become more and more interesting.

Anyway, the final results are a bunch of IMG files which cover the area as shown above, divided into 1250 tiles. Each tile size is about 2MB, which can be combined with other maps, installed to Mapsource or Basecamp to see the ocean floor. Transfer the map to your device as usual through Mapsource or Basecamp.

Navigasi.net map with ocean depth, just realize ocean depth can reach more than 4km.

Too bad, although these files are possible to combined with bluechart map for Homeport, but unfortunately, ocean depth is not shown in the depth profile tab (maps are shown in homeport). I do not know what went wrong (probably caused by the cgpsmapper process), but if you can find a way to make it work with Homeport, please post it here.

The Layout of the IMG files is shown below, the numbers represent the last four digit of the files. I use excel to make it easier for me.